...follow the manufactures (Boeing and Airbus) recommendation...
I respect what Boeing and Airbus say about their aeroplanes - after all, they built them. However, and it's a big however, they have little experience of actually operating them in a commercial environment - that's where the knowledge of the airlines comes in.
I have a great deal of sympathy for the manufacturers as they almost have to assume that it's a single pilot operation and write the usage instructions down to that level: "Put can right side up, apply tin opener, put contents onto plate, eat contents, dispose of tin, etc." The constant fear of lawyers when Air Oogadooga's Afghani franchise has yet another prang on a 737NG/A320 with a frozen pilot on the controls and the other one praying.
That's one way to run an airline (works for some) - another is to use all the resources available to you, share the workload in critical situations and develop the skills of those who will be looking after your valuable assets in the future... Takes time, money, hard work and trust.